Abstract
The piscicide 3-trifluoromethyl-4-nitrophenol (TFM) has been used to control invasive sea lamprey (Petromyzon marinus) populations in the Great Lakes for almost 60 years. Applied to rivers and streams containing larval lampreys, TFM seldom harms non-target fishes, but the effects of sub-lethal treatments on fish physiology are not well understood. We examined the effects of 9 h exposure to TFM on the stress axis and liver metabolic capacity of rainbow trout (Oncorhynchus mykiss) using in vivo and in vitro approaches. The fish that had been acutely exposed to TFM in vivo had increased plasma cortisol levels at 12 h post-treatment, but TFM exposure did not interfere with in vitro cortisol production in head kidney preparations. Subjecting trout to an acute handling stressor 12 h post-TFM exposure resulted in a relative attenuation of the plasma cortisol and glucose response compared to pre-stress levels. We conclude that routine TFM treatments can lead to elevations of plasma cortisol following exposure, plus a relative dampening of the stress response in rainbow trout, with high cortisol levels lasting at least 12 h post-treatment. Since the ability of the fish to produce cortisol and the liver metabolic capacity were not compromised following TFM exposure, it is likely that their ability to cope with other stressors is not altered in the long-term.
Highlights
The piscicide, 3-trifluoromethyl-4-nitrophenol (TFM), has been used for almost 60 years to control invasive sea lamprey (Petromyzon marinus) populations in the Great Lakes [1]
The goal of the present study was to establish if exposure to sub-lethal, environmentally relevant, concentrations of TFM affect the physiology of the rainbow trout, with a specific focus on the hypothalamic-pituitary-interrenal (HPI) axis, which mediates the stress response of fishes, and on liver metabolic capacity, since the liver is involved in detoxification of pesticides
The present study shows that in vivo exposure of rainbow trout to TFM, mimicking a typical lampricide treatment, caused an increase in plasma cortisol levels that persisted following the TFM treatment, but had no effect on head kidney cortisol production in vitro
Summary
The piscicide (lampricide), 3-trifluoromethyl-4-nitrophenol (TFM), has been used for almost 60 years to control invasive sea lamprey (Petromyzon marinus) populations in the Great Lakes [1]. TFM applications are conducted in larval sea lamprey nursery streams and rivers, usually every 2–5 years, to reduce the numbers of parasitic juveniles that migrate to the Great Lakes, where they feed on economically important fishes [2]. TFM is applied at 1.2–1.5 times the 9 h LC99.9, the minimum lethal concentration (MLC) needed to kill 99.9% of the larval sea lamprey [1]. The corresponding concentrations of TFM in the water seldom result in acute toxicity to non-target fishes, as the sea lamprey are much. Effects of TFM on the stress response and liver metabolic capacity in rainbow trout
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